The present invention relates to the treatment of vascular disease by either surgery or percutaneous angioplasty and stenting. More particularly, the invention relates to a system that reduces macro- and micro-embolization during the treatment of vascular stenosis.
A variety of surgical and non-surgical angioplasty procedures have been developed for removing obstructions from blood vessels. Balloon angioplasty utilizes a balloon-tipped catheter which may be inserted within a stenosed region of the blood vessel. By inflation of the balloon, the stenosed region is dilated. Surgery involves either removing the plaque from the artery or attaching a graft to the artery so as to bypass the obstructing plaque. Other techniques, such as atherectomy, have also been proposed. In atherectomy, a rotating blade is used to shave plaque from an arterial wall.
One problem common with all of these techniques is the accidental release of portions of the plaque or thrombus, resulting in emboli which can lodge elsewhere in the vascular system. Such emboli are, of course, extremely dangerous to the patient, frequently causing severe impairment of the distal circulatory bed. Depending upon the vessel being treated, this may result in a stroke or myocardial infarction or limb ischemia.
Vascular filters or embolism traps for implantation into the vena cava of a patient are well known, being illustrated by, for example, U.S. Pat. Nos. 4,727,873 and 4,688,553. Additionally, there is a substantial amount of medical literature describing various designs of vascular filters and reporting the results of the clinical and experimented use thereof. See, for example, the article by Eichelter and Schenk entitled xe2x80x9cProphylaxis of Pulmonary Embolism,xe2x80x9d Archives of Surgery, Vol. 97, August 1968, pp. 348 et seq. See, also, the article by Greenfield, et al., entitled xe2x80x9cA New Intracaval Filter Permitting Continued Flow and Resolution of Embolixe2x80x9d, Surgery, Vol. 73, No. 4, pp. 599-606 (1973).
Vascular filters are used, often during a postoperative period, when there is a perceived risk of a patient encountering a pulmonary embolus resulting from clots generated at the surgical site or the like. As a typical use of vascular filters, the filter is mounted in the vena cava to catch large emboli passing from the surgical site to the lungs.
The vascular filters of the prior art are usually permanently implanted in the venous system of the patient, so that even after the need for the filter has abated, the filter remains in place for the lifetime of the patient, absent surgical removal. U.S. Pat. No. 3,952,747 describes a stainless steel filtering device which is permanently implanted transvenously within the inferior vena cava. The filtering device is intended to treat recurrent pulmonary embolism. U.S. Pat. No. 4,873,978 describes a catheter device comprising a catheter body having a strainer mounted at it distal end. The strainer is shiftable between an opened configuration where it extends substantially across the blood vessel to entrap passing emboli, and a closed configuration where it retains the captured emboli during removal of the catheter. A mechanism actuable at the proximate end of the catheter body allows selective opening and closing of the strainer. Typically, the strainer is a collapsible cone having an apex attached to a wire running from the distal end to the proximate end of the catheter body.
Permanent implantation is often deemed medically undesirable, but it has been done because vascular filters are implanted in patients primarily in response to potentially life threatening situations. Accordingly, the disadvantages of permanent implantations of a vascular filter are often accepted.
To avoid permanent implantation, it would be highly desirable to provide an apparatus and method for preventing embolization associated with conventional surgery and angioplasty procedures. In particular, it would be desirable to provide a device which could be located within the vascular system to collect and retrieve portions of plaque and thrombus which have dislodged during the surgery or angioplasty procedure.
It is an object of this invention to provide a vascular filter system for reducing macro- and micro-embolization.
It is also an object of the invention to provide a vascular filter system which is readily removable from the vascular system, or elsewhere, of a patient when the filter is no longer needed.
It is a further object of the invention to provide a vascular filter system having a configuration which does not require hooks to penetrate and grip the blood vessel walls, so that the implantation results in less blood vessel injury.
It is a yet further object of the invention to provide a vascular filter system of very low profile which is part of a guidewire and can be used in small vessels.
These and other objects of the invention will become more apparent from the description below.
The present invention generally relates to a vascular filter system useful in the surgical or interventional treatment of vascular disease, in particular, a novel percutaneous angioplasty and stenting system useful, for example, in the treatment of carotid stenoses. Macro- and micro-embolization occurs during percutaneous procedures such as angioplasty, which increases the risk of a minor or major stroke. The system of the present invention for reducing macro- and micro-embolization is very useful in helping to prevent the risk of stroke. However, this system would also be useful in any angioplasty or surgical procedure where embolization is a risk.
The vascular filter system of the present invention will decrease embolism while allowing brain, or other distal tissue, perfusion. The filters are incorporated into a guidewire which is used for the entire procedure from crossing a lesion to deploying a stent. In one embodiment the filter consists of a thin membrane attached to the guidewire and supported by fine metal spines. Attachment of the filter membrane to the guidewire allows expansion of the filter membrane with a firm fit inside the artery. The attachment also allows for collapse of the filter membrane at the end of the procedure so it fits tightly against the guidewire and can be withdrawn through the guide catheter. In another embodiment, the filter membrane rests upon or is attached to a basket-like structure, at least one end of which is attached to the guidewire. The filter membrane has a pore size such that blood flow is not impeded when the filter membrane is expanded but micro- and macro-emboli are blocked. Expansion of the filter membrane is aided by the forward flow of blood against the filter. The filter design results in a very low profile so that the initial crossing of the lesion is minimally traumatic. Also, the small diameter and small profile facilitate use of the device in small or larger arteries with minimal or no obstruction of blood flow.